Insulin and Glucagon

Hormones are chemical messengers that tell the cells or tissues to act in a certain way that supports a particular function in the body. Insulin is essential for staying alive.

When we hear the word insulin or glucagon, the first organ that pops up in our mind does the pancreas, the pancreas is the organ that secretes insulin and glucagon and both are said to be working in a balanced way which plays a vital role in regulating blood sugar levels in our bodies. The pancreas is the only organ in the body that secretes an enzyme which is insulin. Insulin and glucagon in return maintain a state which is known as homeostasis, which can be defined as an equal balance or the conditions inside the body being steady and balanced.

Before we get into the detailing of insulin, glucagon let's understand the concept of blood sugar.

Insulin and Glucagon Secretion 

We get most of our energy from the food that we eat which through a process is broken down inside the body now the carbohydrates that we get from food are converted into glucose inside the body and glucose is a simple sugar that serves as a vital source of energy. The very amount of glucose present in the body determines the blood sugar levels which are a measure of how effectively the blood uses glucose. The working of blood sugar varies throughout the day, it can be high after we consume a High carb or high-fat meal and might also drop if we do not consume anything at all or eat food that does not have minimum level or requirements of the carbohydrates, fiber and proteins that a body requires.

Function of Insulin and Glucagon

Insulin is a hormone that is responsible for allowing glucose in the blood to enter cells, which provides them with the energy to function. A lack of insulin plays an important role in the development of diabetes. 

The human body needs blood glucose i.e blood sugar in required amounts for function and proper metabolism of the body. The body takes carbohydrates from food and converts them into glucose i.e a simple form of sugar and this sugar plays a very vital source of energy in the body. Body blood sugar level measures how effectively our body is using glucose. Both insulin and glucagon hormone maintain this glucose level in the body, they are secreted by the pancreas and thus referred to as pancreatic endocrine hormones. 

In case the body is not able to convert enough glucose, blood sugar levels remain high. Insulin helps the cell absorb glucose and reduces blood glucose levels by providing glucose to the body. But in case blood sugar levels are low, then the pancreas releases glucagon. Glucagon commands the liver to release stored glucose, which causes an increase in blood sugar levels. 

Insulin Secretory Pathway

Insulin secretion is a process in the human body that gives a response when blood glucose levels in the blood increase. It is known that insulin facilitates the entry of glucose into the cells. The pancreatic beta cells act as a self-contained system to secrete insulin in response to changes in the level of blood glucose concentration, in order to maintain glucose homeostasis inside the body. The normal fasting blood sugar/glucose level in the human body is between 80mg/100mL and 90mg/100mL. This leads to a decrease in the level of insulin. Insulin is produced in the pancreas and is synthesized in the pancreas within the beta cells i.e beta-cells of the islets of Langerhans.

Mechanisms of Insulin Action and Insulin Resistance 

The mechanism of insulin is pretty straightforward but the usage of different terms might make it confusing for some people, now we already know how to break down the process that takes place in the body so the cells glucose for energy but most of them are unable to use glucose without the help of insulin now what insulin does is that it gives glucose access to the cells by attaching it to the insulin receptors on the cells which are present throughout the body instructing them to open up and grant entry to glucose then a  spike in insulin gives signals to the liver that blood glucose is high then the liver absorb glucose and changes it into storage molecules called glycogen. The same glucagon instructs the liver to convert the glycogen back to glucose in the blood sugar levels drop. Other than the regulation of blood sugar insulin also supports healing after an injury by delivering amino acids to the muscles, thus it is also said in diabetic patients that a low level of production of insulin or secretion results in the delay of healing when a person is injured.

Glucagon: From the above sentences we already know that the liver stores glucose to supply the cells during periods of low blood sugar, by storing glucose the liver makes sure that the levels of glucose in the body remain steady between meals and during sleep. During low levels of blood glucose, glucagon instructs the liver to convert glycogen to glucose so that there is an abundance in availability of glucose in the bloodstream. 

With this we can understand that incident and glucagon work in a cycle, while glucagon interacts with the liver to increase blood sugar on the other hand insulin reduces blood sugar by helping the cells use glucose when required by the body.

Insulin's Role in the Human Body 

Insulin plays a very crucial role in various functioning of the body and they are:

1. They maintain the level of glycogen synthesis.

2. They maintain a level of lipid synthesis inside the body.

3. They also play a crucial role during the esterification process of fatty acids.

4. Insulin regulates how the body uses and stores glucose and fat present in the body.

5. Insulin maintains blood glucose levels by instructing the liver and muscle and fat cells to take in glucose from the blood.

6. An increase or decrease in the concentration of insulin leads to the secretion of hydrochloric acid by parietal cells in the stomach.

Glucagon Secretory Pathway

Glucagon is a type of peptide hormone, produced by alpha cells of the pancreas. It works to raise the concentration of glucose and fatty acid in the bloodstream and is considered to be the main catabolic hormone of the body. It is also used as a medication to treat a number of health conditions. Its function is opposite to that of insulin, which lowers the extracellular glucose levels in the body.  It is produced from proglucagon, encoded by the GCG gene. The pancreas other function is to release glucagon when the amount of glucose in the bloodstream is too low i.e if blood glucose level decreases. 

Glucagon causes the liver to participate in glycogenolysis: it is a process of converting stored glycogen into glucose, which is further released into the bloodstream. High blood glucose levels, on the other hand, stimulate the release of insulin into the bloodstream. Insulin allows glucose to be taken up and used by insulin-dependent tissues present in the body.

The Function of Glucagon Hormone

Glucagon plays an active role in the body during various metabolic activities, they are

1. They instruct the liver to break down glycogen to be released into the blood as glucose

2. They help in activating the gluconeogenesis process i.e the process of conversion of amino acids or (certain non-carbohydrate carbon substrates) into glucose

3. They also break down stored fat triglycerides into fatty acids for use as fuel by cells for performing various metabolic activities.

Broken Balance:

Regulating the body’s blood sugar requirements is quite a feat; however, when this balance is disturbed, certain metabolic and physical disorders arise. These include type 1 and type 2 diabetes. When the body starts producing too much insulin, the cells stop absorbing too much glucose. Which leads the liver to produce too little glucose. This condition leads to a condition called hypoglycemia, where blood sugar levels are dangerously low.

On the other hand, too little insulin can lead to a condition called hyperglycemia, which is characterized by high blood sugar. If this problem is not treated, it can lead to a potentially dangerous condition known as diabetic coma.

MCQ Based on Insulin and Glucagon

1. Which Cell of Pancreas Produces Insulin Hormone:

1. Alpha-cells

2. Beta-cell

3. Gyma-cell

Answer: (b)

2. Which Cell of Pancreas Produce Glucagon Hormone:

1. Alpha-cell 

2. Beta-cell

3. Gymsa-cell

Answer: (a) 

3. Normal Blood Glucose Level of Human Body is:

1. 80mg/100ml

2. 100mg/120ml

3. 120mg/1150ml

Answer: (a)

4. Insulin is produced in response to the following reasons:

1. Increased blood sugar

2. Decreased blood sugar

3. Normal blood sugar

Answer: (a) 

Insulin is an essential hormone for controlling blood sugar and energy absorption.

Insulin is a chemical messenger. The pancreas is the main source of insulin in the body. Clusters of cells in the pancreas which are called islets cells produce the hormone and determine the amount based on blood glucose levels in the body.

When the glucose level goes higher, more insulin goes into production to balance sugar levels in the blood. Insulin also assists in breaking down fats or proteins for energy.

The same goes when blood sugar levels are too low, the pancreas releases glucagon which instructs the liver to release stored glucose, which then causes a rise in blood sugar.

Islet cells in the pancreas release both insulin and glucagon and the pancreas contain plenty of these cells individually or in clusters, the different islet cells include beta cells which are responsible for the release of insulin and alpha cells which are responsible for glucagon.